In recent years, more compact video tape recorders (VTRs) have been made available. Especially, 8-mm VTRs are realized in a greatly reduced size with a diminished weight for use with 8-mm-wide magnetic tape.
With the development of compact and light-weight VTRs, VTRs have been introduced into use which comprise a camera unit and a VTR unit as an assembly. It is also possible to realize a portable image reproduction system which comprises a liquid-crystal television set and a VTR in the form of an assembly. Further reduced sizes are severely required of such VTRs.
Accordingly, Unexamined Japanese Patent Publication SHO. No. 61-271648 discloses a VTR which is variable for different modes in the depthwise length along the direction of insertion of the cassette as shown in FIGS. 41 and 42.
The proposed VTR comprises a head cylinder 11 having a rotary magnetic head and mounted on a main chassis 1, a reel chassis 2 provided on the main chassis 1 and slidable toward or away from the head cylinder 11, and a supply reel support 21 and a take-up reel support 22 which are mounted on the reel chassis 2. The reel chassis 2 is driven by a chassis drive mechanism (not shown) coupled to a loading motor on the main chassis 1.
FIG. 41 shows the recorder in a standby mode, in which the reel chassis 2 is partially projected from the main chassis as indicated at A. In this state, a tape cassette 150 is loaded on the reel supports 21, 22 on the reel chassis 2.
FIG. 42 shows the recorder in a play mode, in which the reel chassis 2 has been slidingly moved toward the head cylinder 11, which is in turn partly positioned in an opening B of the cassette 150. In this state, the magnetic tape is wound around the head cylinder 11 for recording or reproducing signals.
Thus, the depthwise length of the VTR can be reduced from L.sub.1 to L.sub.2 as illustrated. This renders the recorder convenient to carry about.
The VTR of the size variable type described includes a mechanism mounted on the reel chassis for pressing a pinch roller against a capstan with the magnetic tape positioned therebetween. The pinch roller pressing mechanism is operated as associated with the movement of the reel chassis.
An intermittent rotation mechanism is provided between the loading motor and the chassis drive mechanism for transmitting the power of the motor to the drive mechanism during the loading of the reel chassis and blocking power transmission to the drive mechanism after the completion of loading. Further a cam mechanism comprising a face cam is provided between the loading motor and the pinch roller pressing mechanism for driving the pressing mechanism through the rotation of the face cam to move the pinch roller to a position close to the capstan and press the pinch roller against the capstan by the subsequent rotation of the loading motor.
A tape loading mechanism is mounted on the main chassis for withdrawing the magnetic tape from the cassette and winding the tape around the head cylinder. The tape loading mechanism comprises guide rails mounted on the main chassis around the head cylinder, tape leaders slidably fitted in the respective guide rails, drive rings disposed around the head cylinder, and means for connecting the tape leaders to the respective drive rings. The connecting means includes a spring. The drive rings are coupled to the loading motor via a train of gears.
When the motor is started to drive the drive rings, the tape leaders move along the guide rails to wind the tape around the head cylinder. The motor excessively rotates after each leader has reached the limit position of its movement on the guide rail, thereby stretching the spring, which in turn acts to hold the leader at the limit position under pressure.
On the other hand, a swing idler mechanism is mounted on the reel chassis for driving the pair of reel supports. The rotation of a capstan motor is transmitted to either one of the reel supports through the swing idler.
Unexamined Japanese Patent Publication SHO. 61-145756 discloses a VTR including a cassette holder assembly which comprises a cassette holder biased upward by springs and liftably supported on a reel chassis by a holder lift mechanism comprising link means.
The link means includes a cam follower in engagement with a cam face on the main chassis. With the movement of the cam follower relative to the cam face, the cassette holder is held in its lowered position on the reel chassis against the action of the springs during the movement of the reel chassis but is freed from the restraint and raised by the springs when the reel chassis has advanced to a limit position the greatest distance away from the head cylinder.
However, the conventional VTRs described above have the following problems.
Conventionally it is necessary to provide between the loading motor and the pinch roller pressing mechanism a face cam of great lift for moving the pinch roller along the entire path of its movement, whereas the provision of the face cam makes the VTR large-sized and entails another problem in that the friction occurring at the cam face increases the power required for pressing the pinch roller.
With the conventional cassette holder assembly, the cam face included therein needs to be formed over a large distance along the main chassis in accordance with the distance of movement of the reel chassis. This similarly entails the problem of making the VTR large-sized and necessitating increased power for driving the reel chassis.
The load on the motor for driving the conventional tape loading mechanism is low while moving the tape leaders but suddenly increases when subsequently stretching the spring in the connecting means for holding each leader at the limit position under pressure. Accordingly, the motor must be of large capacity to realize the operation during a short period at the final stage of tape loading. Consequently, there is the problem that the motor needs to be large-sized and requires an increased drive voltage.
With the conventional VTR, the swing idler is free to swing and unstable in position while the capstan motor is at a stop, so that in actuality, the idler is generally engaged with either one of the reel supports. Consequently, when the magnetic tape is withdrawn from the cassette by the leaders with the movement of the reel chassis, the pull on the tape exerts a torque on the reel supports, causing the swing idler in engagement with one of the reel supports to engage therewith to a greater extent to brake the reel support against rotation. As a result, the tape is paid off from the other reel support only.
Especially with recording-reproduction systems of greatly reduced size such as 8-mm VTRs, the magnetic tape is wound around the head cylinder through a large angle so that the friction between the head cylinder and the magnetic tape is great. If the tape is paid off from only one of the reel supports for tape loading as stated above, the friction is likely to cause damage to the tape.